G(r,t) analysis method

G(r,t)解析法

菊地 龍弥  

Kikuchi, Tatsuya

In recent years, we have been developing a method for calculating the real space functions, G(r,t) and G(r,E), from the dynamic structure factor, S(Q,E). G(r,t) is van Hove's space-time correlation function which is a function in real space and time. G(r,E) is Fourier-transformed function of S(Q,E) only about spatial axis. Those functions are important to express local motions of atoms and molecules directly. However, the calculations of real-space functions have been hardly performed even though it is so easy mathematically, because it requires spectrum in both high resolution and wide range in Q-E space, which has been difficult to measure in the past. By the progress of the recent neutron sources and spectrometers, the measurements with wide range and high resolution in Q-E space are becoming easy. We measured high-resolution S(Q,E) using AMATERAS spectrometer installed at J-PARC and calculated G(r,t) and G(r,E). We used the maximum entropy method to lower the bias of truncation errors for the calculation of G(r,t). I will introduce the current status and future potential of G(r,t) and G(r,E) calculations, and the results of liquid, glass and crystal.